This invention relates to silicon single crystal pulling devices such as crucibles or dies made of silicon nitride and a method of manufacturing the same.
As a well-known method of manufacture of silicon single crystals used as wafers for semiconductor devices, there is the so-called CZ (Czochralski) method. In this method, silicon is melted in a container (for instance a crucible), and a cylindrical single crystal of silicon is pulled up by rotating a seed crystal. The silicon melting container used in this CZ method is usually made of quartz glass. When a quartz glass container is used, however, silicon and quartz glass are reactive with each other at a temperature about equal to the melting temperature of silicon, and oxygen is trapped in the melted silicon. Therefore, about 2.times.10.sup.18 atoms/cm.sup.3 of oxygen is dissolved in the precipitated silicon. The oxygen dissolved in silicon acts as nuclei of various crystal defects to deteriorate the crystal properties of the silicon single crystal. When this single crystal silicon is processed to produce a semiconductor device, the electric properties thereof are extremely impaired.
Meanwhile, it has been proposed to use silicon nitride for melting silicon because of the fact that silicon nitride has a limited unactivity with silicon. As silicon nitride, there are porous silicon nitride obtainable by a reactive sintering process and high density silicon nitride obtainable by a hot press process However, in the reactive sintering process polyvinyl alcohol or the like is used as a binder, while in the hot press process MgO, AlN, Y.sub.2 O.sub.3 or the like is used as a sintering promoter. This binder or promoter is inevitably introduced as impurity into the sintered silicon nitride. For this reason, if the melting of silicon and pull-up of silicon single crystal are effected using a container which is made of such silicon nitride, the impurity contained in the sintered silicon nitride is dissolved in the silicon single crystal to extremely deteriorate the crystal properties thereof.